Newbie questions about print layout (Photon Mono)

[ednadolski]

Unlike the etched pockets (which are great, Ed), with 3-d printing, trying out different ideas has a turnaround time of hours rather than weeks, and costs pennies rather than dollars.  And the possibilities for custom pockets with integral support hardware are virtually endless.  My mind is positively racing with ideas for covered hoppers parts, tank car end frames with custom saddles, etc.   

Yep, every change to a photoetch design would require a new photo tool mask, not to mention the trans-Atlantic shipping rates and times -- all while hoping not to have made some kind of error that would have to repeat the whole process in order to correct. The 3D option really opens up a lot of doors.

Ed

[GaryHinshaw]

More experiments.  I tried a first cut at a coupler box lid that I thought I could make press fit into the box, but the tolerances are quite good enough to allow that.  The concept was a pair of straps across the bottom of the box, and then a lid with an integral post that captures the coupler and press fits between the straps:



Suffice it to say, the press fit was not great, so I won't dwell on it.  Instead, I drew up a new concept with another lid that also has an integral post, but now has two tabs: one forward and one back that, in theory, will snap into corresponding slots in the box:



The first draft of this design is printing now.    I'll continue this idea in a different thread if it looks promising.  The drawing above is just a box that could be integrated into a larger drawing for a specific set of cars or locos.

[GaryHinshaw]

In an even more experimental vein, I tried printing some walkway platforms to see if they could compete with an etching.  I actually expected the experiment to fail outright, i.e., not even to print.  In fact, when I fired up the printer last night, I went to bed and dreamed about all the ways it would fail and leave a mess in the resin vat.   Much to my surprise though, it actually printed to completion.  The result is not usable as is, but it is somewhat encouraging.  At the very least, it gives me a way to rapid prototype etch designs so that the process is more efficient.

The first part was an attempt to more or less match the hole pattern in the GMM etch.  In setting up the print I tried two vertical orientations for the platform and both printed to completion, but both had issues with warping, more so in the squat orientation.   Here are some shots:



You can see a bit of pixilation in the hole pattern, but it is not especially noticeable in person.





Surprisingly, the part is not especially fragile, but it is quite flexible, so it sags a bit under its own weight (last shot).  For reference, the walkway itself is 0.2 mm (0.008 in) thick and the L frame along the long edge is 0.4 mm (0.016 in) on a side, so quite petite.  I'm going to try beefing up the dimensions a bit, reducing the hole size slightly, and possibly curing it a bit longer.  It might actually work!   

[Chris333]

That walkway is crazy!  Don't know about the mono, but my Photon parts all tend to grow a little bit due to the light bleed around the pixels.

[wazzou]

You can get an awful lot of those walkways on a sheet of PE.

[SkipGear]

Impressive. It's fun seeing just how far you can push these things. Warp on thin parts is inevitable. Design it with a slight bit of frame around it might help. As you thicken the part, the holes may begin to close up naturally from the bloom Chris is talking about. Honestly, over curing seems to make them warp more. I kept the handrails a bit under cured just to keep them a little flexible and more durable.

[narrowminded]

I kept the handrails a bit under cured just to keep them a little flexible and more durable.

Keep in mind that the material cures in natural light so even painted, not overdone to not lose the fine dimensions, it would be a good idea to expect the material to fully cure over time.

I have faith that as the chemists work on these resins somebody will come up with one that's a little tougher.  I understand that the resins currently available with some flexibility still become brittle over time.  I have some to try but haven't yet.

[timwatson]

Some insights I've gained.

3d Printing pro has a great tutorial series on supporting models. He's considered one of the pioneers of getting really good supports that don't leave dimples.
https://www.youtube.com/watch?v=8xolVj0izVo&t=321s

Siraya Blu will give great details and be durable enough for model railroad applications. I mix it regularly with Elegoo grey. The grey makes it more brittle so depending on use you can go a 1 part grey to 3 parts Blu.

Here is Hon30 track printed with the Sirya Blu and Elegoo grey (code 40 rail).
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I hope that helps some.

[John]

Great summary Tim .. I like 3d Printing Pro's videos as well .. and have adopted most of his suggestions

[GaryHinshaw]

Thanks for the resin suggestion, Tim.  I'll be very interested to try that combo!  Do you have any exposure guidelines for that blend?

Interesting choice of penny too.  I assume it's not a copper one?

[timwatson]

@GaryHinshaw it's a real steel penny (1943) - trying to be closer to my era you know!

I'll attach my resin settings. Siraya Blu takes quite a bit longer to cure, so it lengthens curing time compared to the more brittle resins. I also post cure in water and UV light. I'm doing a switch stand test now and I'll post what that looks like when I get a chance.

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[GaryHinshaw]

Thanks @timwatson !  I'll give that a try.  Is that for a colour Photon, or Mono?

[timwatson]

I have the original Photon. I've had it about 2 years now. I got it shortly after there started to be some really wonderful and interesting things being done on TRW.

@John I just realized one of your posts prompted me to check out the 3d printing pros videos. Funny how that info comes back to you when it's effective.

[GaryHinshaw]

Ok, so the Mono should be a bit faster.  BTW, could you elaborate on curing in water??  Thx.

[GaryHinshaw]

Hi @timwatson - one more follow up if I may: is this the Siraya Blu that you're using:

https://www.amazon.ca/Blu-1kg-Precise-Resolution-Printing/dp/B089SLXDFH/ref=sr_1_5?dchild=1&keywords=siraya+blu&qid=1609626263&s=industrial&sr=1-5

Confusingly, they also have a Blu in "Clear V2", which doesn't strike me as "Blu"...  I see they also have an ABS-like non brittle grey:

https://www.amazon.ca/Affordable-Curing-Non-Brittle-Printing-Resin/dp/B07VBM4Z7Q/ref=sr_1_6?dchild=1&keywords=siraya+blu&qid=1609626263&s=industrial&sr=1-6

Do we know how that compares to Elegoo grey?